Image inspection apparatus, image inspection method, and control program of image inspection apparatus

ABSTRACT

An image inspection apparatus for inspecting an output image on a recording medium by scanning the output image as a scanned image includes an inspection reference image generator to generate an inspection reference image using data of an output-target image; an image inspection unit to determine whether the scanned image includes a defect by comparing a difference between the inspection reference image and the scanned image with a given threshold; and a threshold determiner to determine the given threshold. The threshold determiner computes a difference between the inspection reference image and the scanned image. The threshold determiner determines the given threshold based on the difference between the scanned image and the inspection reference image.

This application is a continuation application of U.S. application Ser.No. 14/026,393, filed Sep. 13, 2013, which claims priority pursuant to35 U.S.C. §119 to Japanese Patent Applications Nos. 2012-203583, filedon Sep. 14, 2012, and 2013-165585, filed on Aug. 8, 2013, in the JapanPatent Office. The entire contents of the above-identified applicationsare incorporated herein by reference.

BACKGROUND

1. Technical Field

The present invention relates to an image inspection system and an imageinspection method, and more particularly to setting of inspectionthresholds used for determining defects in image.

2. Background Art

Conventional inspections of printed matter such as printed papers areconducted by visual inspection, but inspection apparatuses have beenintroduced to conduct the inspections as a post-processing operation ofthe offset printing. As for the inspection apparatus, the printedmatters are visually inspected by an operator to select a printed matterhaving satisfactory image quality, and then the selected printed matteris scanned to generate a master image to be used as a reference image.The master image and inspection target printed matter are compared witheach other by scanning the inspection target printed matter, and basedon difference between the master image and the inspection target, defectof the inspection target printed matter can be determined.

However, the printing apparatuses of digital to press such as imageforming apparatuses using electrophotography typically print images witha small volume, and also print different images for each page (i.e.variable printing), in which generating a master image from printedmatter as a reference image is not efficient. In this type of imageforming apparatuses, the master image can be generated from print datato efficiently conduct the inspection for the variable printing.

In this image inspection process, the defect of printed matter can bedetermined based on the above mentioned difference level. Specifically,scanned images prepared by scanning sheets printed with images and themaster image generated from the print data are compared, in whichpositions and sizes of comparing images are matched and then thecomparing images are compared for each pixel based on a given threshold.

JP-2008-003876-A discloses an image inspection process for an inkjetprinter, which can verify inspection precision for the image inspection.Specifically, defects that may likely occur for the inkjet printer areartificially printed on sheets, the sheets having printed with theartificial defects are inspected, and then it is verified whether theinspection can be conducted effectively.

The above mentioned threshold used for comparing the images affect theinspection precision, therefore effective thresholds need to be set forhigh precision inspection. JP-2008-003876-A discloses a configuration todetermine whether the inspection is conducted effectively usingthresholds such as thresholds set in advance, in which suitablethresholds are not set automatically.

SUMMARY

In one aspect of the present invention, an image inspection apparatusfor inspecting an image output on a recording medium by scanning theoutput image as a scanned image Is devised. The image inspectionapparatus includes an inspection reference image generator to obtaindata of an output-target image used by the image forming apparatus toconduct an image forming operation, and to generate an inspectionreference image using the data of the output-target image, theinspection reference image to be used for an image inspection of thescanned image; an image inspection unit to determine whether the scannedimage includes a defect based on a comparison result obtained bycomparing a difference between the inspection reference image and thescanned image with a given threshold; and a threshold determiner todetermine the given threshold. The threshold determiner controlsgeneration of the inspection reference image having a normal imagecondition to be used for determining the given threshold. The thresholddeterminer computes a difference between the inspection reference imageand the scanned image obtained by scanning a threshold setting imageprepared by adding an artificial defect to the inspection referenceimage. The threshold determiner determines the given threshold based onthe difference between the scanned image and the inspection referenceimage.

In another aspect of the present invention, a method of inspecting animage output on a recording medium by an image forming apparatus Isdevised. The method comprising the steps of: obtaining data of anoutput-target image input to the image forming apparatus; forming athreshold setting image on the recording medium using the image formingapparatus, the threshold setting image prepare-able by adding anartificial defect to the output-target image; generating an inspectionreference image using the data of the output-target image; scanning thethreshold setting image formed on the recording medium to obtain ascanned image of the threshold setting image; computing a differencebetween the scanned image and the inspection reference image bycomparing the scanned image and the inspection reference image; anddetermining a threshold based on the difference between the scannedimage and the inspection reference image, the determined threshold to becompared with the difference between the scanned image and theinspection reference image to determine whether the scanned imageincludes a defect.

In another aspect of the present invention, a non-transitorycomputer-readable carrier medium storing a program that, when executedby a computer, causes the computer to execute a method of inspecting animage output on a recording medium by an image forming apparatus isdevised. The method comprising the steps of obtaining data of anoutput-target image input to the image forming apparatus; forming athreshold setting image on the recording medium using the image formingapparatus, the threshold setting image prepare-able by adding anartificial defect to the output-target image; generating an inspectionreference image using the data of the output-target image; scanning thethreshold setting image formed on the recording medium to obtain ascanned image of the threshold setting image; computing a differencebetween the scanned image and the inspection reference image bycomparing the scanned image and the inspection reference image; anddetermining a threshold based on the difference between the scannedimage and the inspection reference image, the determined threshold to becompared with the difference between the scanned image and theinspection reference image to determine whether the scanned imageincludes a defect.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages and features thereof can be readily obtained and understoodfrom the following detailed description with reference to theaccompanying drawings, wherein:

FIG. 1 shows a schematic configuration of an image forming systemincluding an inspection apparatus according to an example embodiment;

FIG. 2 shows an example block diagram of a hardware configuration of theinspection apparatus according to an example embodiment;

FIG. 3 shows an example block diagram of an engine controller, a printengine and an inspection apparatus according to an example embodiment;

FIG. 4 shows a schematic mechanical configuration of a print processingunit according to an example embodiment;

FIG. 5 shows an example block diagram of master image processing unitaccording to an example embodiment;

FIG. 6 is a flowchart of process of a threshold determination processaccording to an example embodiment;

FIGS. 7A, 7B and 7C show examples of output images used for a thresholddetermination process according to an example embodiment;

FIG. 8 shows an example of setting of artificial defects according to anexample embodiment;

FIG. 9 shows an example of a computation result of discrete thresholdcomputed for a plurality of artificial defects according to an exampleembodiment;

FIG. 10 is a flowchart of process of computing discrete thresholdaccording to an example embodiment;

FIGS. 11A and 11B show examples of threshold selection screens accordingto an example embodiment;

FIG. 12 shows another example of threshold selection screen according toan example embodiment;

FIGS. 13A and 13B show schematic configurations of systems according toanother example embodiment;

FIG. 14 shows a schematic configuration of a system according to anotherexample embodiment;

FIG. 15 schematically shows a process of comparing images for inspectionaccording to an example embodiment; and

FIG. 16 schematically shows an example of threshold setting according toan example embodiment.

The accompanying drawings are intended to depict exemplary embodimentsof the present invention and should not be interpreted to limit thescope thereof. The accompanying drawings are not to be considered asdrawn to scale unless explicitly noted, and identical or similarreference numerals designate identical or similar components throughoutthe several views.

DETAILED DESCRIPTION

A description is now given of exemplary embodiments of the presentinvention. It should be noted that although such terms as first, second,etc. may be used herein to describe various elements, components,regions, layers and/or sections, it should be understood that suchelements, components, regions, layers and/or sections are not limitedtherefore because such terms are relative, that is, used only todistinguish one element, component, region, layer or section fromanother region, layer or section. Thus, for example, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings of the present invention.

In addition, it should be noted that the terminology used herein is forthe purpose of describing particular embodiments only and is notintended to be limiting of the present invention. Thus, for example, asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. Moreover, the terms “includes” and/or “including”, when usedin this specification, specify the presence of stated features,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

Furthermore, although in describing views shown in the drawings,specific terminology is employed for the sake of clarity, the presentdisclosure is not limited to the specific terminology so selected and itis to be understood that each specific element includes all technicalequivalents that have a similar function, operate in a similar manner,and achieve a similar result. Referring now to the drawings, apparatusesor systems according to example embodiments are described hereinafterwith reference to FIGS. 1 to 25.

In this disclosure, an image forming system includes an inspectionapparatus, in which a master image and an scanned image obtained byscanning an image output by an image forming operation are compared toinspect an output (e.g., printed image) of the image forming operation,and based on the a comparison result, thresholds used to determinedefect in an image, matched to inspection precision desired by a user,can be settable easily and preferably.

FIG. 1 shows an example configuration of an image forming systemaccording to an example embodiment. As shown in FIG. 1, the imageforming system includes, for example, a digital front end (DFE) 1, anengine controller 2, a print engine 3 and an inspection apparatus 4.Based on a received print job, the DFE 1 generates bitmap data, which isimage data to be output (i.e., output-target image), and outputs thegenerated bitmap data to the engine controller 2.

Based on the bitmap data received from the DFE 1, the engine controller2 controls the print engine 3 to conduct an image forming operation.Further, the engine controller 2 transmits the bitmap data received fromthe DFE 1 to the inspection apparatus 4, wherein the bitmap data is usedas data of original information for preparing an inspection referenceimage to be used for inspection at the inspection apparatus 4 when theinspection apparatus 4 inspects an output result of an image formingoperation of the print engine 3.

Under the control of the engine controller 2, the print engine 3conducts an image forming operation on a recording medium such as paperusing the bitmap data, and scans an output paper such as a paper printedwith an image using a scanner, and inputs the scanned image data to theinspection apparatus 4. The recording medium may be, for example, asheet such as paper, film, plastic sheet, and any material that can beused for outputting (i.e., forming) an image by an image formingoperation. Based on the bitmap data input from the engine controller 2,the inspection apparatus 4 generates a master image. Then, theinspection apparatus 4 compares the scanned image data, input from theprint engine 3, and the generated master image to conduct an imageinspection of output image, in which the inspection apparatus 4 is usedas an image inspection apparatus.

A description is given of a hardware configuration of the enginecontroller 2, the print engine 3 and the inspection apparatus 4according to an example embodiment with reference to FIG. 2. Further, asfor the inspection apparatus 4, engines for scanner and printer may beadded to the hardware configuration shown in FIG. 2. FIG. 2 shows ablock diagram of an example hardware configuration of the inspectionapparatus 4. The engine controller 2 and the print engine 3 may have ahardware configuration similar to the inspection apparatus 4 shown inFIG. 2.

As shown in FIG. 2, the inspection apparatus 4 can be configuredsimilarly to information processing apparatuses such as general servers,and personal computers (PC), or the like. Specifically, the inspectionapparatus 4 includes a central processing unit (CPU) 10, a random accessmemory (RAM) 20, a read only memory (ROM) 30, a hard disk drive (HDD)40, and an interface (I/F) 50, connectable to each other via a bus 90.Further, the 1/F 50 is connectable to a liquid crystal display (LCD) 60,an operation unit 70, and a specific device 80.

The CPU 10 is a computing processor or unit which controls theinspection apparatus 4 as a whole. The CPU 10 can be configured withvarious types of processors, circuits, or the like, such as a programmedprocessor, a circuit, and an application specific integrated circuit(ASIC), used singly or in combination. The RAM 20 is a volatile memory,to which data or information can be written and read at high speed, andis used as a working memory when the CPU 10 processes data orinformation. The ROM 30 is a non-volatile memory used as a read onlymemory, and stores programs such as firmware or the like. The HDD 40 isa non-volatile storage device, to and from which data or information canbe written and read, and stores operating system (OS), management orcontrol software programs, application software programs, various data,or the like.

The I/F 50 can be used to connect various types of hardware and networkto the bus 90, and controls such connection. The LCD 60 is a userinterface to display information, with which the status of theinspection apparatus 4 can be checked by a user. The operation unit 70is a user interface such as a keyboard, a mouse, etc., with whichinformation can be input to the inspection apparatus 4 by the user.

The specific device 80 may be disposed as hardware to conduct a specificcapability or function for each of the engine controller 2, the printengine 3 and the inspection apparatus 4. For example, as for the printengine 3, the specific device 80 may be a plotter to conduct an imageforming operation on sheets, and a scanner to scan images output on thesheets. Further, as for the engine controller 2 and the inspectionapparatus 4, the specific device 80 may be a specific computing circuitto conduct high speed image processing, and the specific device 80 maybe, for example, an application specific integrated circuit (ASIC).

In the above hardware configuration, software programs stored in astorage area such as the ROM 30, the HDD 40, or an optical disk can beread and loaded to the RAM 20, and the CPU 10 runs such programs tocontrol various units, with which a software-executing controller can beconfigured. With a combination of such software-executing controller andhardware, a functional block to operate the engine controller 2, theprint engine 3 and the inspection apparatus 4 can be configured. In anexample embodiment, at least one of the units is implemented as hardwareor as a combination of hardware/software.

FIG. 3 shows an example block diagram of the engine controller 2, theprint engine 3 and the inspection apparatus 4. As shown in FIG. 3, theengine controller 2 includes, for example, a data obtainer 201, anengine control unit 202 and a bitmap transmitter 203. Further, the printengine 3 includes, for example, a print processing unit 301 and ascanner 302. Further, the inspection apparatus 4 includes, for example,a scanned image obtainer 401, a master image processing unit 402, aninspection control unit 403 and an inspection unit 404. The inspectionunit 404 can be used as an image inspection unit that compares imagesfor inspection.

Upon obtaining the bitmap data from the DFE 1 by the data obtainer 201,the engine control unit 202 and the bitmap transmitter 203 are operated.The bitmap data is information of pixels composing an image to be outputby an image forming operation, and the data obtainer 201 can function asa pixel information obtainer. Based on the bitmap data transferred fromthe data obtainer 201, the engine control unit 202 instructs the printengine 3 to conduct an image forming operation, in which the enginecontrol unit 202 can function as an output execution control unit. Thebitmap transmitter 203 transmits the bitmap data, obtained by the dataobtainer 201, to the inspection apparatus 4.

The print processing unit 301 obtains the bitmap data input from theengine controller 2, conducts an image forming operation to a sheet, andoutputs a printed sheet. Therefore, the print processing unit 301 canfunction as an image forming apparatus. The print processing unit 301can use any types of image forming mechanism including, for example, theelectrophotography, the inkjet method, or the like. The scanner 302scans an image formed on the sheet by conducting a printing operation bythe print processing unit 301, and outputs scanned data to theinspection apparatus 4. The scanner 302 is, for example, a line scannerdisposed along a transport route of sheet output by the print processingunit 301, in which the scanner 302 scans the transported sheet face toread an image formed on the sheet.

A description is given of mechanical configurations of the printprocessing unit 301 and the scanner 302 with reference to FIG. 4. Asshown in FIG. 4, the print processing unit 301 includes, for example,image forming units 106BK, 106M, 106C, 106Y and a transport belt 105 ofan endless movement unit, in which the image forming units 106BK, 106M,106C, 106Y are disposed along the transport belt 105, which is referredto as the tandem type. Specifically, the image forming units 106BK,106M, 106C, 106Y (electrophotography processing units) are disposedalong the transport belt 105 from the upstream side of a transportdirection of the transport belt 105. An intermediate transfer image isformed on the transport belt 105, and transferred to a recording mediumsuch as a sheet 104, which is separated and fed from a sheet tray 101using a sheet feed roller 102 and a separation roller 103.

The internal configuration is common for the image forming units 106BK,106M, 106C, 106Y except color of toner image, which means the imageforming unit 106BK forms black image, the image forming unit 106M formsmagenta image, the image forming unit 106C forms cyan image, and theimage forming unit 106Y forms yellow image. Hereinafter, the imageforming unit 106BK is described as the representative of the imageforming units 106BK 106M, 106C, 106Y. Each members composing the imageforming units 106BK 106M, 106C, 106Y may be attached with BK, M, C, Y asrequired.

The transport belt 105 is an endless belt extended by a drive roller 107and a driven roller 108. The drive roller 107 can be rotated by a drivemotor. The drive motor, the drive roller 107 and the driven roller 108can be collectively function as a drive unit for the transport belt 105which is the endless movement unit.

When forming images, the image forming unit 106BK transfers black tonerimage to the rotating transport belt 105. The image forming unit 106BKincludes, for example, a photoconductor drum 109BK used as aphotoconductor, a charger 110BK disposed near the photoconductor drum109BK, a development unit 112BK, a photoconductor cleaner, and adecharger 113BK. Further, an optical writing unit 111 irradiates lightfor each of the photoconductor drums 109BK, 109M, 109C, 109Y(hereinafter, photoconductor drum 109).

When forming images, an outer face of the photoconductor drum 109BK ischarged uniformly by the charger 110BK in a dark environment, and thenan electrostatic latent image for black image is formed on thephotoconductor drum 109BK by irradiating light from a light source forblack image in the optical writing unit 111. The development unit 112BKdevelops the electrostatic latent image using black toner, and thenblack toner image is formed on the photoconductor drum 109BK.

The black toner image is transferred to the transport belt 105 at atransfer position of the photoconductor drum 109BK and the transportbelt 105 by a transfer unit 115BK, in which the photoconductor drum109BK and the transport belt 105 may contact or be the closest with eachother. With this transfer, the black toner image is formed on thetransport belt 105. Upon completing the transfer of black toner image,the photoconductor cleaner removes toner remaining on the outer face ofthe photoconductor drum 109BK, and then the photoconductor drum 109BK isdecharged by the decharger 113BK to prepare for a next image formingoperation.

The transport belt 105 transferred with the black toner image by theimage forming unit 106BK is transported to the image forming unit 106M,next to the image forming unit 106B, by rotating the transport belt 105.Similar to the image forming process at the image forming unit 106BK,the image forming unit 106M forms magenta toner image on thephotoconductor drum 109M, and the magenta toner image may besuperimposed and transferred on the black toner image.

The transport belt 105 having the transferred black toner image andmagenta toner image is then transported to the image forming units 106C,106Y. Similar to the image forming unit 106BK, cyan toner image formedon the photoconductor drum 109C, and yellow toner image formed on thephotoconductor drum 109Y may be superimposed and transferred on theblack toner image and magenta toner image, with which the intermediatetransfer image of full color is formed on the transport belt 105.

The sheet 104 stacked in the sheet tray 101 is fed from the top sheet,and the intermediate transfer image formed on the transport belt 105 istransferred on the sheet 104 at a transfer position that the transportbelt 105 and the sheet 104 contact or be the closest with each other inthe transport route, with which an image is formed on the sheet 104. Thesheet 104 formed with the image is transported to a fusing unit 116 tofuse the image on the sheet 104, and then ejected from the image formingapparatus.

In the fusing unit 116, the toner image transferred on the sheet 104 isfused by heat, in which water included in the sheet 104 is vaporizedwhen the sheet 104 is passing through the high temperature fusing unit116, with which the sheet 104 shrinks and therefore the image size onthe sheet 104 may be come smaller than the image size of original image.When the scanner 302 scans the shrink sheet 104, the scanned imagesmaller than the original image may be generated.

Further, when the duplex printing is conducted, the sheet 104 having thefused image is transported to an inverting route to invert the faces ofthe sheet 104, and then the sheet 104 is transported to the transferposition again. The sheet 104 having the fused image on one face or bothfaces is transported to the scanner 302. Then, the scanner 302 scans oneface or both faces, with which a scanned image, which is an inspectiontarget image, is generated.

A description is given of the inspection apparatus 4 by referring FIG. 3again. The scanned image obtainer 401 obtains the scanned image datagenerated by scanning the sheet face by the scanner 302 in the printengine 3, and inputs the scanned image data as an inspection targetimage to the inspection unit 404. As described above, the master imageprocessing unit 402 obtains the bitmap data input from the enginecontroller 2, and generates a master image as an inspection referenceimage to be compared with the inspection target image. Therefore, basedon the output-target image, the master image processing unit 402 is usedas an inspection reference image generator that generates the masterimage as the inspection reference image to be used for inspecting thescanned images. The generation process of master image by the masterimage processing unit 402 will be described later.

The inspection control unit 403 controls the inspection apparatus 4 as awhole, and each unit in the inspection apparatus 4 is operated under thecontrol of the inspection control unit 403. Further, in an exampleembodiment, the inspection control unit 403 includes, for example, amaster image generation controller 403 a, an image comparison inspectioncontroller 403 b, a threshold determination processing unit 403 c and auser interface (UI) controller 403 d as shown in FIG. 3. The inspectionunit 404 is used as an image inspection unit that compares the scannedimage data, input from the scanned image obtainer 401, and the masterimage, generated by the master image processing unit 402, to determinewhether a desired image forming operation is conducted. The inspectionunit 404 may be configured with the above mentioned ASIC or the like tocompute a great amount of data with high speed processing.

A description is given of the master image processing unit 402 withreference to FIG. 5. FIG. 5 shows an example block diagram of the masterimage processing unit 402. As shown in FIG. 5, the master imageprocessing unit 402 includes, for example, a binary/multi-valueconverter 421, a resolution level converter 422, a color converter 423and a master image outputting unit 424. The master image processing unit402 can be devised as the specific device 80 (see FIG. 2) devised by acombination of hardware and software such as the ASIC controlled bysoftware. The inspection unit 404 and the master image processing unit402 can be configured using the ASIC as described above. Further, theinspection unit 404 and the master image processing unit 402 can beconfigured using a software module executable by the CPU 10.

The binary/multi-value converter 421 conducts a binary/multi-valueconverting process to a binary format image expressed binary such ascolor/non-color to generate a multi-valued image. The bitmap data isinformation input to the print engine 3. The print engine 3 conducts animage forming operation based on binary format image for each color ofcyan, magenta, yellow, black (CMYK). Because the scanned image data,which is the inspection target image, is a multi-valued image composedof multi-gradient image of the three primary colors of red, green andblue (RGB), a binary format image is initially converted to amulti-valued image by the binary/multi-value converter 421. Themulti-valued image is, for example, an image expressed by 8-bit for eachCMYK.

Further, the print engine 3 conducts an image forming operation based onbinary format image for each of CMYK, and the master image processingunit 402 includes the binary/multi-value converter 421 but not limitedhereto. For example, when the print engine 3 conducts an image formingoperation based on multi-valued image, the binary/multi-value converter421 can be omitted.

The resolution level converter 422 conducts a resolution levelconversion process to match a resolution level of multi-valued imagegenerated by the binary/multi-value converter 421 to a resolution levelof the scanned image data (i.e., inspection target image). Because thescanner 302 generates scanned image data, for example, with theresolution level of 200 dots per inch (dpi), the resolution levelconverter 422 converts a resolution level of multi-valued imagegenerated by the binary/multi-value converter 421 to 200 dpi.

The color converter 423 obtains the image having converted with theresolution level by the resolution level converter 422 and conducts acolor converting process. Because the scanned image data is RGB-formatimage as described above, the color converter 423 converts theCMYK-format image having converted with the resolution level by theresolution level converter 422 to the RGB-format image, with which amulti-valued image of 200 dpi expressed with 8-bit for each of RGB(total 24 bits) for each pixel is generated.

The master image outputting unit 424 outputs the master image, generatedby using the binary/multi-value converter 421, the resolution levelconverter 422 and the color converter 423, to the inspection controlunit 403. Based on the master image obtained from the master imageprocessing unit 402, the inspection control unit 403 instructs theinspection unit 404 to conduct an image comparing process to obtain acomparison result.

Referring back to FIG. 4, the inspection unit 404 compares the scannedimage data and the master image expressed with 8-bit for each of RGB(total 24 bits) as described above for each corresponding pixel, andcomputes difference of pixel values for each of RGB for each pixel.Based on the comparison of the computed difference and a threshold, theinspection unit 404 determines whether a defect occurs to the scannedimage data. Therefore, the inspection unit 404 can function as an imageinspection unit to determine defect of the scanned image data based ondifference of the inspection reference image and the scanned image data.Further, the difference computed for each of pixels can be correlatedfor each of pixel positions and can be configured as a differentialimage.

Further, the difference and the threshold can be compared by theinspection unit 404 as follows. For example, values of the differencecomputed for each of pixels are summed for a given area of an image as atotal value, and the total value is compared with the threshold, whichis set to be compared with the total value. The given area for summingvalues of the difference of each of pixels is, for example, a 20-dotsquare area. In an example embodiment, the threshold is a value set forthe total difference value of the given area (hereinafter, defectdetermination unit area) obtainable by summing values of the difference.The inspection unit 404 can output information of position of the defectdetermination unit area on an image having a total difference exceedingthe threshold, wherein this position information can be used asinformation indicating presence of defect in the scanned image data. Theposition information in the image is defined by, for example, coordinateinformation on the image.

When comparing the scanned image and the master image, the scanned imageis divided into a plurality of areas as shown in FIG. 15. The inspectionunit 404 superimposes each divided area to a corresponding area of themaster image to compute a difference of pixel value of each pixel suchas difference of density. Further, a position of superimposing thedivided area to the master image is shifted left/right and up/down todetermine a position that the computed difference becomes the smallestand the smallest difference is used as a comparison result. Each one ofthe divided areas shown in FIG. 15 can be used as the above describeddefect determination unit area.

Further, the above described threshold can be provided by registersetting to the inspection unit 404 configured as, for example, ASIC. Theinspection control unit 403, which is configured by executing a programusing the CPU 10, writes a threshold, set as shown in FIG. 17, to theregister provided to designate a threshold for the inspection unit 404,with which the above described threshold can be set.

Further, in another method, each pixel is determined as normal or defectbased on a comparison result of the difference computed for each pixeland the threshold, and the count number of pixels determined as defectand the threshold set for the count number are compared.

In the system according to an example embodiment, when settingthresholds used for the image comparing process by the inspection unit404, thresholds matched to inspection precision, which may be desired bya user, can be set easily, and therefore, each of the modules includedin the inspection control unit 403 can be used to determine the abovementioned threshold using each unit of the inspection apparatus 4. Adescription is given of a process of setting the threshold withreference to FIG. 6.

FIG. 6 is a flowchart of process of setting threshold according to anexample embodiment. As shown in FIG. 6, when setting the threshold,under the control of the engine controller 2, the print engine 3conducts a printing operation for images used for setting thresholds(hereinafter, referred to as threshold setting image) (S601). FIGS. 7Ato 7C show examples of threshold setting images according to an exampleembodiment. As for the threshold setting images, FIG. 7A shows referenceimage pattern 701, which is an image having normal image condition notadded artificial defects, and the reference image pattern is used todetermine thresholds. As shown in FIG. 7A, the reference image pattern701 can be drawn and formed in 4 rows in the horizontal direction or theX direction, and 5 lines in the vertical direction or the Y directionfor given color mark. The images of FIG. 7A can be output as a firstimage using the print engine 3 under the control of the enginecontroller 2.

By contrast, FIGS. 7B and 7(c) show threshold setting images prepared byadding a plurality of different artificial defects to the abovedescribed reference image of normal image condition. FIG. 7B show imagesprepared by adding artificial defects having different color densitiesto the above described reference image pattern (hereinafter,density-changed defect pattern 702). As shown in FIG. 7B, thedensity-changed defect pattern 702 can be prepared by adding differentartificial defects to each one of marks arranged in the X direction andthe Y direction. The images of FIG. 7B can be output as a second imageusing the print engine 3 under the control of the engine controller 2.

As for the density-changed defect pattern, each mark arranged in the Xdirection is added with artificial defects of different colors, and eachmark arranged in the Y direction is added with artificial defects ofdifferent densities. Therefore, the images of FIG. 7B are images addedwith a plurality of artificial defect having different colors anddensity levels. FIG. 8 shows an example of information referred by theengine control unit 202 of the engine controller 2 when outputting thedensity-changed defect pattern 702 shown in FIG. 7B (hereinafter,density-changed defect pattern information). Further, information of thedensity-changed defect pattern of FIG. 8 can be stored, for example, ina storage included in the engine controller 2 such as the RAM 20, ROM30, HDD 40, and/or an external storage.

In FIG. 8, PC, PM, PY and PK are values indicating colors such as C, M,Y, K for the pattern. As shown in FIG. 8, as for the density-changeddefect pattern information, each pattern arranged in 4 rows in the Xdirection and 5 lines in the Y direction is set with color informationof artificial defects. For example, as a pattern for the firstline/first row, PC is added with d₁, and as for other M, Y, K in thefirst line, the same value of color are added with as artificial defect,in which d₁ is added to PM at the second row, to PY at the third row,and to PK at the fourth row, with which artificial defects having colorsdifferent from the original pattern can be prepared.

Further, as shown in FIG. 8, adding values can be changed such as +d₁,+d₂, +d₃ - - - in the Y direction, in which the greater the value of nof d_(n), the greater the density, which means, in the Y direction,color density becomes thicker by adding values of artificial defects.The change of density is indicated in FIG. 7B by using line patternssuch as dot line, dashed line, or the like.

When outputting the density-changed defect pattern shown in FIG. 7B, theengine control unit 202 obtains settings for an range for changingdensity, and determines a value of d_(n) shown in FIG. 8 based on theobtained settings for the range. The settings for the range may includevalues that may be set for the engine control unit 202 in advance, orset manually by a user when outputting the density-changed defectpattern.

The d_(n) can be obtained using the following formula (1) by setting thelower limit d_(m) and the upper limit d_(M) for the settings of therange.

d _(n) =d _(m)+¼(d _(M) −d _(m))×n  (1)

Based on the computation using the above formula (1), the range of fromd_(m) to d_(M) can be divided equally, for example, by five values of d₁to d₅, and can be used as the adding values of density.

FIG. 7C show images prepared by adding artificial defects havingdifferent line width to the above described reference image pattern(hereinafter, width-changed defect pattern 703). Similar to thedensity-changed defect pattern, as shown in FIG. 7C, the width-changeddefect pattern 703 can be prepared by adding different artificialdefects to each one of marks arranged in the X direction and the Ydirection. Similar to the images of FIG. 7B, the images of FIG. 7C areimages added with a plurality of artificial defect different in colorand width. The images of FIG. 7C can be output as a third image usingthe print engine 3 under the control of the engine controller 2. Similarto the density-changed defect pattern 702, as for the width-changeddefect pattern 703, each mark arranged in the X direction is added withartificial defects of different colors, and each mark arranged in the Ydirection is added with artificial defects of different width.

Similar to the density-changed defect pattern, the engine control unit202 changes width of artificial defects within a set range for changingwidth of artificial defects shown in FIG. 7C. The range of changingwidth can be computed using the above formula (1) as d_(n) of width ofartificial defects. Further, the engine control unit 202 stores thecomputed d_(n) to be used for a later processing.

Further, in an example embodiment, the engine control unit 202 cangenerate bitmap data used for an image forming operation of the patternsshown in FIG. 7A to FIG. 7C, but the DFE 1 can generate bitmap data.

In the process at S601, the engine controller 2, the print engine 3 andthe inspection apparatus 4 respectively conduct the above describedoperations, in which the engine controller 2 transmits the bitmap datato the inspection apparatus 4, and data of the scanned image, generatedin the print engine 3 by scanning the output sheet using the scanner302, is input to the inspection apparatus 4. Then, when setting thethresholds, based on the bitmap data input from the engine controller 2,the inspection apparatus 4 generates a master image based on bitmap dataof the first image (S602 a), and selects and obtains data of scannedimage of the second image and the third image (S602 b).

In the process at S602 a, among bitmap data of the first, second andthird images input from the engine controller 2, the master imagegeneration controller 403 a of the inspection control unit 403 controlsthe master image processing unit 402 to generate a master image only forthe first image. The master image is used as the inspection referenceimage as described above. The master image is also referred to as anormal reference image used for inspection, and the normal referenceimage is used as the inspection reference image for the preparing theabove described threshold setting image.

Further, in the process at S602 b, the image comparison inspectioncontroller 403 b of the inspection control unit 403 controls the scannedimage obtainer 401 to discard the scanned image data of the first imagefrom the scanned image data of the first, second and third images inputfrom the print engine 3, and obtains the scanned image of the secondimage and the third image. The scanned image data is image data obtainedby scanning the above described threshold setting image, wherein scannedimage data is also referred to as defect scanned image.

Then, the image comparison inspection controller 403 b of the inspectioncontrol unit 403 controls the inspection unit 404 to compare the abovedescribed master image of first image and the scanned image of thesecond and third images (image comparing process) to compute the abovedescribed difference for each of the second image and the third image toobtain a differential image (S603). In S603, a difference between themaster image and the scanned image data is computed for each of aplurality of artificial defects having different colors and levels shownin FIG. 7B and FIG. 7C.

Upon obtaining the differential image for the second image and the thirdimage with respect to the master image, as explained with reference toFIGS. 7A to 7C, the threshold determination processing unit 403 c of theinspection control unit 403 computes a threshold to detect an artificialdefect artificially added in each of marks arranged in rows and lines asdefect (S604). In the process of S604, as shown in FIG. 9, thresholdsuch as th11, th12 - - - can be computed for each of marks arranged in 4rows in the X direction and 5 lines in the Y direction. In S604, basedon the difference generated for each one of a plurality of artificialdefects having different colors and levels, a threshold to be used fordetermining each one of the plurality of artificial defects as defectcan be computed, and the each computed threshold is referred to asdiscrete threshold. Further, information shown in FIG. 9 can be stored,for example, in a storage included in the inspection unit 404 such asthe RAM 20, ROM 30, HDD 40, and/or an external storage.

FIG. 9 shows an example of a table including discrete thresholds. In anexample embodiment, a discrete threshold is set for each mark includedin the second image and the third image. Therefore, the table shown asFIG. 9 can be generated for each of the second image and the thirdimage.

A description is given of a detail of S604 (FIG. 6) with reference toFIG. 10. As shown in FIG. 10, the threshold determination processingunit 403 c sets a starter threshold (S1001) at first. The starterthreshold is a threshold that any types of defect are not extracted asdefect, which means that even if a total difference value for the defectdetermination unit area is great, a value greater than the totaldifference value for the defect determination unit area is set as thestarter threshold, with which no defect is determined as defect.

Upon setting the starter threshold, the threshold determinationprocessing unit 403 c controls the inspection unit 404 to conduct adefect determination process based on the set threshold (S1002). InS1002, a defect determination process is conducted for each areadisplaying each mark shown in FIG. 7A to FIG. 7C. By contrast, in anormal determination process, a defect determination process isconducted for an entire image. Therefore, the number of target pixelsbecomes different between the determination at S1002 and thedetermination for the normal determination process, therefore thepopulation parameter of computed difference valued becomes different. Tocope with the change of population parameter, the threshold to beapplied at S1002 is adjusted in view of a ratio of the number of pixelsof entire image and the number of pixels of an area displaying eachmark. Further, the starter threshold set at S1001 can be set to a valuecorresponding to the number of pixels of an area displaying each mark.

If each area displaying a mark is determined as current defect based onthe determination result of S1002 (S1003: YES), the thresholddetermination processing unit 403 c registers or sets a currently-usedthreshold as a threshold for the area determined as current defect tothe table shown in FIG. 9 (S1004). With this processing, each discretethreshold such as th11, th12 and so on shown in FIG. 9 can beregistered.

Upon completing S1004, the threshold determination processing unit 403 cchecks whether a threshold is set for all of areas (S1005). If thethreshold is set for all of areas as shown in FIG. 9 (S1005: YES), theprocess ends. By contrast, if no area is determined as current defectwhen S1002 is conducted (S1003: NO), or if the threshold is not yet setfor all of areas (S1005: NO), the threshold determination processingunit 403 c changes a value of the threshold to increase the probabilityto be determined as defect (S1006), and repeats the process from S1002.

In an example embodiment, the threshold determination processing unit403 c can change values of threshold gradually to increase theprobability to be determined as a defect, and repeats the defectdetermination process until all of areas are determined as defect. Withthis processing, as explained with reference to FIGS. 7B and 7C,thresholds matched to an actual defect determination process can bedetermined based on thresholds used for extracting various artificialdefects having different levels. Further, in an example embodiment,because the defects can be determined based on the scanned image datagenerated by the scanner 302, thresholds matched to the images scannedreal time by the scanner 302 can be set.

Further, as described above, the threshold applied at S1002 is differentfrom the threshold to determine a defect for an entire image. Therefore,if a threshold set at the concerned timing is multiplied by the numberof pixels and the multiplied threshold is used as a threshold at S1002,a threshold set to a table at S1004 is a threshold set at the concernedtiming. By contrast, if a threshold set at the concerned timing is usedas a threshold at S1002, a threshold set to a table at S1004 is athreshold obtained by multiplying the threshold set at the concernedtiming by the number of pixels.

Further, in the defect determination process, a ratio of the number ofpixels having difference greater than a given value with respect to thetotal number of pixels can be used as information for the defectdetermination process. If the ratio such as percentage is set as athreshold, the same threshold can be used even if the populationparameter of pixels, to be inspected, changes.

Upon completing the process of S604, the UI controller 403 d controls adisplay unit to display a graphical user interface (GUI), which is usedby a user to set a threshold, and the inspection control unit 403receives a selection result input by a user's operation (S605). The GUIdisplayed in S605 is referred to as a threshold selection screenhereinafter, and FIG. 11A and FIG. 11B show examples of thresholdselection screens. The threshold selection screens shown in FIG. 11A andFIG. 11B can be displayed on a display unit such as the LCD 60 connectedto the inspection apparatus 4. FIG. 11A shows an initial screen of GUIdisplayed in S605, which means a screen before a user's selectionoperation.

As shown in FIG. 11A, the threshold selection screen displays images ofthe density-changed defect pattern and the width-changed defect patterndescribed with reference to FIGS. 7B and 7C. These images can bedisplayed using, for example, the second image and the third imageobtained by the scanned image obtainer 401. The user can select one ormore marks to be identified as defect on the screen shown in FIG. 11A.

When selecting the mark on the screen shown in FIG. 11A, the useroperates the screen, but the mark is selected by looking the outputsheet (i.e., not selected on the screen), in which the user candetermine the defect based on the defect actually output on the sheet.FIG. 11B shows an example screen when images to be identified as defectare selected by the user. As shown in FIG. 11B, the mark selected by theuser is displayed on the screen with high-lighted condition such asencircling frame.

When the mark is selected as described above, the UI controller 403 dobtains the selection result, and the threshold determination processingunit 403 c can set a threshold to detect each mark as defect byreferring the table shown in FIG. 9. Specifically, when the UIcontroller 403 d receives the user's selection at S605, the thresholddetermination processing unit 403 c extracts a discrete threshold,corresponding to the defect selected by the user shown in FIG. 11B, fromthe table shown in FIG. 9. In this process, the UT controller 403 drecognizes one or more defects selected by an operation to the screenshown in FIG. 11A by a user.

Specifically, when one or more marks are selected as defect as shown inFIG. 11B, the threshold determination processing unit 403 c obtainsinformation of arrangement position of the selected defect on the image,and identifies the arrangement in X direction and the arrangement in Ydirection indicated in the table of FIG. 9. Then, the thresholddetermination processing unit 403 c extracts information of thresholdcorresponding to the arrangement position of the selected defect such asth11, th21 and so on from the table shown in FIG. 9.

Upon extracting the discrete thresholds for the selected defects (FIG.11B) from the table of FIG. 9, the threshold determination processingunit 403 c determines a finally-set threshold based on the extracteddiscrete thresholds (S606). In S606, among the extracted discretethresholds corresponding to the marks selected by the user asto-be-determined as defect, the threshold determination processing unit403 c determines one of the discrete thresholds as the finally-setthreshold, in which a discrete threshold having the strictest thresholdis determined as the finally-set threshold. When the strictest thresholdis set as the finally-set threshold, the greater number of marks can bedetermined as defect. The threshold determined with this process can bestored as the threshold setting as shown in FIG. 16, and when theinspection unit 404 conducts an inspection by comparing images, athreshold can be provided to the inspection unit 404 by writing thethreshold as a register value by the inspection control unit 403.

Upon determining the finally-set threshold, the threshold determinationprocessing unit 403 c determines whether re-adjustment is required basedon the user's operation (S607), in which the UI controller 403 obtainsan operation instruction input by the user. In S607, the thresholddetermination processing unit 403 c controls a display unit such as theLCD 60 connected to the inspection apparatus 4 to display a screen forselecting whether the re-adjustment is required, and determines whetherthe re-adjustment is required based on the user's operation to thescreen.

If the re-adjustment is not required (S607: NO), the thresholddetermination processing unit 403 c ends the process. By contrast, ifthe re-adjustment is required (S607: YES), the threshold determinationprocessing unit 403 c instructs the engine controller 2 to repeat thesteps from S601 and controls the inspection apparatus 4, in which asdescribed above, the inspection control unit 403 designates a range ofchanging density and/or width of the density-changed defect pattern orthe width-changed defect pattern. Specifically, the thresholddetermination processing unit 403 c can designate d_(n) for the markhaving the maximum value d_(M) and the minimum value d_(m) for eachdiscrete threshold extracted at S605.

As described above, the d_(n) computed for each mark can be stored inthe storage included in the engine controller 2 such as the RAM 20, ROM30, HDD 40, and/or the external storage. Therefore, the thresholddetermination processing unit 403 c can designate “d_(n)” for each ofthe density-changed defect pattern and the width-changed defect patternto the engine control unit 202 by only notifying a position in the Ydirection of a mark corresponding to the above described maximum valueand minimum value.

Further, at S605, a discrete threshold can be extracted for each of thedensity-changed defect pattern and the width-changed defect pattern.Therefore, the threshold determination processing unit 403 c designatesd_(n) for a mark corresponding to the maximum value and the minimumvalue of each discrete threshold extracted at S605 for each of thedensity-changed defect pattern and the width-changed defect pattern.

When the process of S601 is to be conducted repeatedly, the mark addedwith the artificial defect corresponding to the maximum value and theminimum value of the discrete threshold, extracted by the process atS605 by already conducting the threshold setting process once, can beformed as the density-changed defect pattern and the width-changeddefect pattern. By conducting the process of FIG. 6 for the second imageand the third image, the threshold can be set more precisely.

In the system of an example embodiment, images displaying defects havingchanged the defect level step-wisely as shown in FIGS. 7B and 7C areprepared. By conducting the defect determination process by changing thethresholds step-wisely, discrete thresholds that can detect each ofdefects having step-wisely changed defect levels can be obtained. Then,the user checks a sheet printed with a given pattern with eyes to selectone or more marks to be determined as defect, and determines thefinally-set threshold based on the discrete threshold correlated to theselected marks. With this processing, when the image inspection isconducted based on a comparison result obtained by comparing an imagegenerated by scanning an image output by an image forming operation anda master image, the setting of threshold used for determining the defectcan be conducted easily and preferably based on the comparison result.

Further, in the above described example embodiment, when setting thethresholds, for example, a printing operation of images shown in FIGS.7A to 7C is conducted. With this configuration, for example, a processof changing a range of to-be-set threshold (e.g. S607 in FIG. 6) can beconducted repeatedly. If the process of changing a range of threshold isnot required, bitmap data of image shown in FIG. 7A is input to themaster image processing unit 402, and a known scan-use chart having theimages similar to the images shown in FIGS. 7B and 7C can be scanned bythe scanner 302 of the print engine 3, with which the above describedoperation can be conducted.

Further, in the above described example embodiment, as shown in FIGS.11A and 11B, the second image and the third image are displayed on ascreen, from which a user can select marks intuitively based on visualinformation displayed on the screen but not limited hereto. For example,a user can select marks from a list shown in FIG. 12, wherein the listincludes position information of marks in the X direction and the Ydirection, which may be indicated as text information.

Further, in the above described example embodiment, as shown in FIGS.7B/7C and FIGS. 11A/11B, the density-changed defect pattern andwidth-changed defect pattern are displayed on the screen by arrangingmarks having different color and levels of artificial defects with agiven order, with which a user can easily select an allowable defect inview of the level of artificial defects. Further, the density-changeddefect pattern and width-changed defect pattern can be displayed on thescreen by arranging marks having different color and levels ofartificial defects randomly (i.e., not arranged with a given order),with which a user can select marks without preconception.

Further, as explained with reference to FIGS. 7B and 7C, in an exampleembodiment, the density-changed defect pattern and the width-changeddefect pattern can be reproduced using a plurality of artificial defectshaving different levels for each of cyan, magenta, yellow and black(CMYK). Because of human perception on colors may differ for eachperson, the level of artificial defects that can be allowed or not foreach one of colors may be different for each person.

For example, as for a relatively pale color such as Y, one user mayallow a mark corresponding to PY+d₄ shown in FIG. 8 (i.e., only a markcorresponding to PY+d₅ is selected as to-be-determined defect) while thesame user may select marks corresponding to from PK+d₁ to PK+d₅ (i.e.,all of marks shown in FIG. 8) as the to-be-determined defect for K. Inthis case, a threshold set for the mark corresponding to PK+d₁ becomesthe strictest value. If this strictest value is applied, the defect of Ythat the user determines as allowable may be determined as defect.

In this case, the inspection unit 404 can set thresholds step-wisely toenhance the user's convenience. Specifically, the finally set thresholdmay include a first threshold and a second threshold, in which the firstthreshold is set to determine defect without confirmation by a user, andthe second threshold is set to determine defect based on a selection ofa user.

In this case, at S605 (FIG. 6), the threshold determination processingunit 403 c extracts the strictest value as a threshold corresponding tothe selected mark for each of artificial defects of each of colors, thatis for each of rows in the table shown in FIG. 9. Then, among thethresholds extracted for each of colors, the threshold determinationprocessing unit 403 c sets a value having a broadest allowable range asthe first threshold, with which a smaller number of defects aredetermined as defect, and sets the strictest value as the secondthreshold, with which a greater number of defects are determined asdefect.

In this processing, if a defect is determined as defect when thethreshold having the broadest allowable range is applied, a user maydetect the same defect as defect by visual confirmation with a higherprobability, therefore the defect is determined as defect without theconfirmation by the user. Further, if a defect is determined as defectwhen the threshold having the narrowest allowable range is applied, itis not clear whether the user may detect the same defect as defect byvisual confirmation, therefore the defect is determined as defect basedon the confirmation by the user, with which the defect determinationprecision can be enhanced.

Further, when the setting process of thresholds is conducted repeatedlyas explained with reference for S607 (FIG. 6), the thresholddetermination processing unit 403 c can designate the value of d_(n)such as d_(m) and d_(M) of d_(n) as the value corresponding to the firstthreshold and the second threshold.

Further, in the above described example embodiment, as explained withreference to FIGS. 11A/11B and S605 (FIG. 6), upon the visualconfirmation of artificial defects by the user, a mark is selected, withwhich the inspection apparatus 4 can determine the finally-set thresholdbased on the threshold corresponding to the selected mark. With thisconfiguration, the allowable level of defect determination can be seteasily based on the user's visual confirmation.

Further, even without the user's selection operation, by setting thethreshold based on a difference between a normal image such as the firstimage shown in FIG. 7A and artificial defect images such as the secondand third images shown in FIGS. 7B and 7C, which are images added withartificial defects, the threshold corresponding to the condition of thescanner 302 can be set. Therefore, by omitting the process of S605 (FIG.6), the threshold can be set automatically based on the differencebetween the master image generated for the normal image and the scannedimage data of the image added with artificial defects.

Further, in the above example embodiment, as shown in FIG. 1, the DFE 1,the engine controller 2, the print engine 3 and the inspection apparatus4 are separate apparatuses with each other. The DFE 1, the enginecontroller 2 and the print engine 3 shown in FIG. 1 can be included inimage forming apparatuses such as printers, which are not image formingapparatuses for commercial printing machines such as productionprinters.

For example, as shown in FIG. 13A, the inspection apparatus 4 can beconnected to a printer having the DFE 1, the engine controller 2 and theprint engine 3. Further, as shown in FIG. 13B, a printer having the DFE1, the engine controller 2, the print engine 3 and the inspectionapparatus 4 can be configured as one printer.

Further, in the above example embodiment, the DFE 1, the enginecontroller 2, the print engine 3 and the inspection apparatus 4 areconnected with each other via a local interface such as universal serialbus (USB), peripheral component interconnect express (PCIe) or the liketo configure the system. However, the inspection apparatus 4 is notrequired to be placed at the same site of the DFE 1, the enginecontroller 2 and the print engine 3, but the inspection apparatus 4 canbe provided as an application for the system, for example, via anetwork.

FIG. 14 shows one example configuration that the function of theinspection apparatus 4 is provided via the network, in which the enginecontroller 2 and the print engine 3 may be connected to the inspectionapparatus 4 via a public line 5 such as the Internet. The enginecontroller 2 and the print engine 3 can transmit information to theinspection apparatus 4 via the public line 5. Further, the inspectionapparatus 4 can transmit an inspection result to the engine controller 2via the public line 5. In this configuration, the inspection apparatus 4is not required at a user site, with which an initial cost of the usercan be reduced.

Further, in the configuration shown in FIG. 14, the user cannot controlthe inspection apparatus 4 directly because the function of theinspection apparatus 4 is provided via the network. In thisconfiguration, the screens shown in FIGS. 11A/11B and FIG. 12 and otherscreens for controlling the inspection apparatus 4 can be displayed onan information processing apparatus such as a personal computer (PC)connectable to the network via a web browser, with which the user canuse the system similar to the above example embodiment.

Further, in the above example embodiment, the first image, the secondimage and the third image are formed on different sheets, but notlimited hereto. For example, the first image, the second image, and thethird image can be formed on the same sheet, in which the master imageprocessing unit 402 generates a master image by extracting an areadisplaying the first image, and further, the scanned image obtainer 401extracts an area displaying the second image and the third image fromthe scanned image, and uses the extracted area as the scanned image datafor the inspection target.

Further, in the above example embodiment, the levels of artificialdefect can be changed by changing the defect density and/or defect range(e.g., width of defect), but not limited thereto. For example, otherparameters of image can be used and changed as required. Further, in theabove example embodiment, each parameter can be changed separately, butparameters can be changed with some combinations.

Further, in the above example embodiment, when the thresholddetermination process is conducted, the modules used for the normalinspection process such as the master image processing unit 402, theinspection unit 404 or the like can be controlled by the master imagegeneration controller 403 a and the image comparison inspectioncontroller 403 b, and the threshold determination processing unit 403 cand the UI controller 403 d can be operated based on informationobtained by the control, with which the modules can collectivelyfunction as a threshold determiner. With this configuration, theconfiguration of apparatus can be simplified by using each moduleeffectively. Further, because the same or similar modules used for thenormal inspection process can be used for the above example embodiment,the threshold can be effectively determined under the same or similarcondition of the normal inspection process, but the configuration is notlimited hereto.

For example, some specific modules can be employed for the master imagegeneration controller 403 a and the image comparison inspectioncontroller 403 b of the above example embodiment, in which a masterimage generation module and an image comparison inspection modulespecifically employed for the threshold determination process can beprovided, which means an inspection reference image generation unit thatgenerates an inspection reference image having normal image condition tobe used for the image inspection, and an image comparison inspectionunit that computes a difference between the scanned image of thethreshold setting image and the inspection reference image can beprovided.

Further, in the above example embodiment, the threshold determinationprocessing unit 403 c and the UI controller 403 d are configured in theinspection control unit 403, but the configuration is not limitedhereto. For example, a specific module for the threshold determinationprocessing unit 403 c and a specific module for the UI controller 403 dcan be provided separately from the inspection control unit 403.

In the above described example embodiment, an image inspection can beconducted by comparing an image obtained by scanning an image output byan image forming operation and a master image, and based on a comparisonresult, setting of threshold used to determine defect can be conductedeasily and preferably.

The present invention can be implemented in any convenient form, forexample using dedicated hardware, or a mixture of dedicated hardware andsoftware. The present invention may be implemented as computer softwareimplemented by one or more networked processing apparatuses. The networkcan comprise any conventional terrestrial or wireless communicationsnetwork, such as the Internet. The processing apparatuses can compromiseany suitably programmed apparatuses such as a general purpose computer,personal digital assistant, mobile telephone (such as a WirelessApplication Protocol (WAP) or 3G-compliant phone) and so on. Since thepresent invention can be implemented as software, each and every aspectof the present invention thus encompasses computer softwareimplementable on a programmable device.

The computer software can be provided to the programmable device usingany storage medium, carrier medium, carrier means, or digital datacarrier for storing processor readable code such as a flexible disk, acompact disk read only memory (CD-ROM), a digital versatile disk readonly memory (DVD-ROM), DVD recording only/rewritable (DVD-R/RW),electrically erasable and programmable read only memory (EEPROM),erasable programmable read only memory (EPROM), a memory card or sticksuch as USB memory, a memory chip, a mini disk (MD), a magneto opticaldisc (MO), magnetic tape, a hard disk in a server, a solid state memorydevice or the like, but not limited these.

The hardware platform includes any desired kind of hardware resourcesincluding, for example, a central processing unit (CPU), a random accessmemory (RAM), and a hard disk drive (HDD). The CPU may be implemented byany desired kind of any desired number of processor. The RAM may beimplemented by any desired kind of volatile or non-volatile memory. TheHDD may be implemented by any desired kind of non-volatile memorycapable of storing a large amount of data. The hardware resources mayadditionally include an input device, an output device, or a networkdevice, depending on the type of the apparatus. Alternatively, the HDDmay be provided outside of the apparatus as long as the HDD isaccessible. In this example, the CPU, such as a cache memory of the CPU,and the RAM may function as a physical memory or a primary memory of theapparatus, while the HDD may function as a secondary memory of theapparatus.

In the above-described example embodiment, a computer can be used with acomputer-readable program, described by object-oriented programminglanguages such as C++, Java (registered trademark), JavaScript(registered trademark), Perl, Ruby, or legacy programming languages suchas machine language, assembler language to control functional units usedfor the apparatus or system. For example, a particular computer (e.g.,personal computer, work station) may control an information processingapparatus or an image processing apparatus such as image formingapparatus using a computer-readable program, which can execute theabove-described processes or steps. In the above described embodiments,at least one or more of the units of apparatus can be implemented inhardware or as a combination of hardware/software. In exampleembodiment, processing units, computing units, or controllers can beconfigured with using various types of processors, circuits, or the likesuch as a programmed processor, a circuit, an application specificintegrated circuit (ASIC), used singly or in combination.

Numerous additional modifications and variations are possible in lightof the above teachings. It is therefore to be understood that, withinthe scope of the appended claims, the disclosure of the presentinvention may be practiced otherwise than as specifically describedherein. For example, elements and/or features of different examples andillustrative embodiments may be combined each other and/or substitutedfor each other within the scope of this disclosure and appended claims.

What is claimed is:
 1. An image inspection apparatus for inspecting animage output on a recording medium by scanning the output image as ascanned image, the image inspection apparatus comprising: an inspectionreference image generator to obtain data of an output-target image usedby the image forming apparatus to conduct an image forming operation,and to generate an inspection reference image using the data of theoutput-target image, the inspection reference image to be used for animage inspection of the scanned image; an image inspection unit todetermine whether the scanned image includes a defect based on acomparison result obtained by comparing a difference between theinspection reference image and the scanned image with a given threshold;and a threshold determiner to determine the given threshold, wherein thethreshold determiner controls generation of the inspection referenceimage having a normal image condition to be used for determining thegiven threshold, wherein the threshold determiner computes a differencebetween the inspection reference image and the scanned image obtained byscanning a threshold setting image prepared by adding an artificialdefect to the inspection reference image, wherein the thresholddeterminer determines the given threshold based on the differencebetween the scanned image and the inspection reference image.